Avon BTO

Monday, July 28, 2008

Almost there

The end of the first season approaches, and I have had the results from 160 tetrads to date- and there are plenty more to come, boith paper and on the web.
lessons learnt?- A lot of people only do things at the last minute- and it is probably better to do things early- certainly in the breeding season.
Identifying juveniles, and providing breeding status generally, has been a novelty for some and is trickier than might at first appear. Luckily someone doing a 10k square usually comes up with proof of confirmed breeding- though there are some slightly embarrasing blanks. But no odds- targetting species next year will fill the gaps.
Overall change in the breeding population since 1992 is also pretty clear; 27 have a significantly (ie more than 10 points increase) wider distribution now than they did; 17, mostly uncommon, species have decline further or gone. 11 new species have appeared, mostly in very small numbers. Quite how much of the wider distribution is caused by the change in methods has yet to be calculated.
There are no surprises, but it is good to have precision about the processes of change, which are, of course, continuous, complex, and driven by a mass of interacting causes. (For those who believe climate might be relevant, the four years 1988-91 of the previous survey had an average annual temperature of 13.9C .The last twelve months have an average of 14.2C).

Once the final figures are in i can look at the breeding season density compared with the winter, and the changes in density since 1994,


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